The overall goal of the proposed project is to provide data concerning the relationships between the anatomically recognized retinal ganglion cell classes and the ganglion cell classes descried in physiological studies and, further, to describe possible correlations between specific morphological and functional characteristics among these cells. The primary technique used to achieve this aim will be electrophophysiological classification of cat retinal ganglion cells by transcleral microelectrode recording followed by intracellular injection of these neurons with horseradish peroxidase. Labeled retinal ganglion cells will subsequently be analyzed morphologically at both the light and electron microscopic level. A number of these structure/function correlations have been previously defined at the light microscopic level; extension of these experiments to the ultrastructural analysis of physiologically characterized retinal ganglion cells is the only direct approach available for defining differences in the pattern and distribution of synaptic input between different classes of ganglion cells. These analyses will also determine if recognizable synaptic patterns are related to specific response characteristics. Despite considerable variability within the "W- cell" class, data obtained in the previous grant period have made it possible to separate retinal W-cells into two mutually exclusive classes that can be defined by both anatomical and functional criteria. A second aim of the proposed grant period is to analyze the visual responses of retinal W-cells quantitatively. These studies are designed to separate retinal W-cells into distinct classes based on objective response criteria and will also provide data similar to those available for retinal X- and Y- cells; data that have proven instrumental in the development of current hypotheses concerning the contribution of these cells to mammalian visual function. With very few exceptions, these data are lacking for retinal W-cells (which comprise nearly 50% of retinal ganglion cells). A final aim of this grant period is to develop an in vitro recording preparation to investigate the mechanisms underlying the visual responses of retinal ganglion cells. The objective of these experiments is to define the synaptic mechanisms that underlie the visual responses of retinal ganglion cells and also to determine the role that the intrinsic properties of these neurons play in defining the response differences between ganglion cell classes. These studies will provide normal data for future comparison with those from abnormal developmental conditions.